Heavily armed police offers arrive on the scene of the
manhunt.Brian
Snyder/REUTERS

An officer aims his gun at
a suspect.Brian
Snyder/REUTERS

A man
is ordered to the ground by police. It is unclear whether he was
later released.Brian
Snyder/REUTERS

Law enforcement officials
stage in a parking lot during a search for the two men suspected
of setting off two explosions during the Boston Marathon in
Watertown, Massachusetts, April 19, 2013.REUTERS/Lucas Jackson

A law
enforcement official checks his rifle during the police
search.Lucas
Jackson/REUTERs

Hospital
officials who treated Suspect 1 suggested he may have been
wearing an explosive device, although they would not confirm
this.